The carbon–oxygen bond length in phenol is slightly less than that in methanol due to 

The bond angle in alcohols is slightly less than the tetrahedral angle (109°-28). It is due to the repulsion between the unshared electron pairs of oxygen. In phenols, the –OH group is attached to sp² hybridised carbon of an aromatic ring. The carbon– oxygen bond length (136 pm) in phenol is slightly less than that in methanol. This is due to (i) partial double bond character on account of the conjugation of unshared electron pair of oxygen with the aromatic ring and (ii) sp² hybridised state of carbon to which oxygen is attached.